Secondary cell activation method, access network device, and communications apparatus and system

ABSTRACT

A secondary cell activation method and apparatus relating to the communications field are described herein. The method may include sending, by an access network device, an activation command to a terminal device, where the activation command indicates activating a secondary cell. The method may also include sending, by the access network device, first configuration information of a first reference signal to the terminal device. Furthermore, the method may include sending, by the access network device, the first reference signal to the terminal device according to the first configuration information, where the first reference signal is used to obtain a channel measurement result of the secondary cell. According to secondary cell activation methods described herein, a flexible and efficient secondary cell activation mechanism can be provided, so as to improve secondary cell activation efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/096208, filed on Jul. 19, 2018, which claims priority toChinese Patent Application No. 201710687908.8, filed on Aug. 11, 2017.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the communications field, and inparticular, to a secondary cell activation method, an access networkdevice, and a communications apparatus and system.

BACKGROUND

Currently, in network deployment of a wireless communications network, acarrier aggregation (CA) technology is used. One access network devicemay have a plurality of different cells, and a terminal device may beconnected to the plurality of different cells of the access networkdevice at the same time. CA means that communication is simultaneouslyperformed on one primary carrier and several secondary carriers insteadof only one carrier in a communication process. Cells aggregated by theterminal device having a carrier aggregation function include oneprimary cell and several secondary cells. In a process of using thesecondary cells, the secondary cells may be activated and deactivatedaccording to a requirement. For example, if no data is transmittedbetween the access network device and the terminal device within a time,the access network device may deactivate a secondary cell. Thedeactivated secondary cell is not used for data transmission between theaccess network device and the terminal device. Subsequently, when dataneeds to be transmitted or a relatively large amount of data is to betransmitted, the access network device activates a secondary cellaccording to a requirement. The activated secondary cell is used againfor data transmission between the access network device and the terminaldevice. Generally, one cell may be corresponding to one carrier set, andthe carrier set includes at least one carrier.

In some approaches, when a terminal device needs to activate a secondarycell, the terminal device needs to send channel state information (CSI)of the secondary cell to an access network device, to activate thesecondary cell. The terminal device usually reports CSI of all cells tothe access network device through a physical uplink control channel(PUCCH) of a primary cell. Specifically, when the terminal devicereceives, in a subframe N, a secondary cell activation command sent bythe access network device, the terminal device adds the CSI of theactivated secondary cell to a CSI report at a preset time (for example,a subframe N+8), and sends the CSI to the access network device. Theterminal device may not obtain a valid CSI measurement value from theCSI report to which the CSI is added at the preset time. In this case,the terminal device needs to fill a special measurement value into theCSI, to notify the access network device that the terminal device doesnot obtain the valid measurement value. The terminal device does notstart to fill a normal CSI measurement value until the terminal devicestarts to obtain the valid CSI measurement value.

Specifically, in a long term evolution (LTE) system, one cellcorresponds to one carrier, and cell activation is carrier activation.In response to an activation command of the access network device, theterminal device measures a cell common reference signal (CRS) to obtainCSI, and reports the CSI to the access network device. The measurementmay be radio resource management (RRM) measurement. However, in somescenarios, configuration information of a CRS is specified in aprotocol, and a sending period and a location are relatively fixed. Inaddition, the terminal device can receive and measure the CRS only whenthe terminal device is synchronized with a to-be-activated cell.Consequently, an existing CRS-based activation method is not flexibleenough, and has relatively low activation efficiency. In addition, theactivation method can be applied only to a system compatible with a CRS,and is not commonly used.

SUMMARY

The present disclosure describes embodiments of a secondary cellactivation method, an access network device, and a communicationsapparatus and system, so that a flexible and efficient secondary cellactivation mechanism can be provided.

To achieve the foregoing objective, the following technical solutionsare used in the embodiments of the present invention.

According to a first aspect, a secondary cell activation method isprovided, including:

-   -   sending, by an access network device, an activation command to a        terminal device, where the activation command is used to        indicate activating a secondary cell;    -   sending, by the access network device, first configuration        information of a first reference signal to the terminal device;        and    -   sending, by the access network device, the first reference        signal to the terminal device according to the first        configuration information, where the first reference signal is        used to obtain a channel measurement result of the secondary        cell.

According to the method, the access network device may send the firstreference signal and the first configuration information of the firstreference signal to the terminal device, so that the terminal deviceperforms channel measurement on the first reference signal according tothe first configuration information. This solution avoids a scenario inwhich a secondary cell can be measured and activated based only on afixedly configured CRS, so as to improve secondary cell activationflexibility, and improve secondary cell activation efficiency.

In an optional design, the first reference signal is located before anavailable second reference signal of the terminal device in time domain,and the second reference signal is configured by using secondconfiguration information; or the first reference signal is locatedbetween two adjacent second reference signals of the terminal device intime domain, and the two adjacent second reference signals areconfigured by using same second configuration information. According tothe method, when there is already the second reference signal configuredby using the second configuration information, the first referencesignal configured by using the first configuration information can betemporarily sent, so that the terminal device quickly responds to theactivation command to measure the secondary cell without affectingcurrent sending of the second reference signal configured by using thesecond configuration information.

In an optional design, the second reference signal is periodic.

In an optional design, the first reference signal is a synchronizationsignal SS or a channel state information reference signal CSI-RS.

In an optional design, when the access network device determines thatthe terminal device is not synchronized with the secondary cell, thereference signal is a synchronization signal. The synchronization signalis configured to perform channel measurement when the secondary cell isactivated, so that the terminal device can still quickly perform channelmeasurement in time and obtain the channel measurement result even ifthe terminal device is in an out-of-synchronization state.Alternatively, when the access network device determines that theterminal device is synchronized with the secondary cell, the referencesignal is a channel state information reference signal. The channelstate information reference signal is of relatively sparse distributionon a resource, and occupies a relatively small quantity of resources.Therefore, the channel state information reference signal is configuredto perform channel measurement when the secondary cell is activated, sothat the access network device can more easily obtain an availableresource used to send the first reference signal, and the terminaldevice can quickly perform channel measurement and obtain the channelmeasurement result.

In an optional design, the activation command includes the firstconfiguration information; or

-   -   the access network device sends the first configuration        information before the activation command; or    -   the activation command includes a first part of the first        configuration information, and the access network device sends a        second part of the first configuration information before the        activation command.

In an optional design, the first configuration information includes atleast one of the following information:

-   -   a reference signal sending indication;    -   a reference signal sending time;    -   a reference signal period;    -   a reference signal time domain resource location;    -   a reference signal frequency domain resource location; and    -   a reference signal configuration index, where the reference        signal configuration index is used to indicate a location of        reference signal configuration information.

In an optional design, the reference signal sending time of the firstreference signal is a relative time difference between a time at whichthe access network device sends the first reference signal and a time atwhich the access network device sends the activation command, or is atime at which the access network device sends the first referencesignal.

In an optional design, before the sending, by the access network device,the first reference signal to the terminal device according to the firstconfiguration information, the method further includes: when adifference between the available second reference signal of the terminaldevice and a current time exceeds a first threshold, determining, by theaccess network device, to send the first reference signal to theterminal device. The method can avoid a signaling waste caused by stillsending the first reference signal when the second reference signal thatcan be used for channel measurement is sent to the terminal device in ashort time after the activation command is sent.

The first threshold is preset, in some embodiments.

In an optional design, the access network device receives the channelmeasurement result from the terminal device.

The first aspect further provides a secondary cell activation method,including:

-   -   receiving, by a terminal device, an activation command from an        access network device, where the activation command is used to        indicate activating a secondary cell;    -   receiving, by the terminal device, first configuration        information of a first reference signal from the access network        device; and    -   receiving, by the terminal device, the first reference signal        according to the first configuration information, and obtaining        a channel measurement result of the secondary cell according to        the first reference signal.

According to the method, the terminal device may receive the firstreference signal and the first configuration information of the firstreference signal from the access network device, so that the terminaldevice performs channel measurement on the first reference signalaccording to the first configuration information. This solution avoids ascenario in which a secondary cell can be measured and activated basedonly on a fixedly configured CRS, so as to improve secondary cellactivation flexibility, and improve secondary cell activationefficiency.

In an optional design, the first reference signal is located before anavailable second reference signal of the terminal device in time domain,and the second reference signal is configured by using secondconfiguration information; or the first reference signal is locatedbetween two adjacent second reference signals of the terminal device intime domain, and the two adjacent second reference signals areconfigured by using same second configuration information.

In an optional design, the second reference signal is periodic.

In an optional design, the first reference signal is a synchronizationsignal or a channel state information reference signal.

In an optional design, the activation command includes the firstconfiguration information; or the terminal device receives the firstconfiguration information before the activation command; or theactivation command includes a first part of the first configurationinformation, and the terminal device receives a second part of the firstconfiguration information before the activation command.

In an optional design, the first configuration information includes atleast one of the following information:

-   -   a reference signal sending indication;    -   a reference signal sending time;    -   a reference signal period;    -   a reference signal time domain resource location;    -   a reference signal frequency domain resource location; and    -   a reference signal configuration index, where the reference        signal configuration index is used to indicate a location of        reference signal configuration information.

In an optional design, the sending time of the first reference signal isa time difference between a time at which the access network devicesends the first reference signal and a time at which the access networkdevice sends the activation command, or is a time at which the accessnetwork device sends the first reference signal.

In an optional design, the terminal device sends the channel measurementresult to the access network device.

According to a second aspect, an access network device is provided,including a transmitter and a processor, where

-   -   the processor is configured to determine first configuration        information of a first reference signal;    -   the transmitter is configured to send an activation command to a        terminal device, where the activation command is used to        indicate activating a secondary cell;    -   the transmitter is further configured to send the first        configuration information of the first reference signal that is        determined by the processor to the terminal device; and    -   the transmitter is further configured to send the first        reference signal to the terminal device according to the first        configuration information, where the first reference signal is        used to obtain a channel measurement result of the secondary        cell.

In an optional design, the first reference signal is located before anavailable second reference signal of the terminal device in time domain,and the second reference signal is configured by using secondconfiguration information; or the first reference signal is locatedbetween two adjacent second reference signals of the terminal device intime domain, and the two adjacent second reference signals areconfigured by using same second configuration information.

In an optional design, if the processor determines that the terminaldevice is not synchronized with the secondary cell, the reference signalis a synchronization signal; or if the processor determines that theterminal device is synchronized with the secondary cell, the referencesignal is a channel state information reference signal.

In an optional design, the activation command includes the firstconfiguration information; or the transmitter sends the firstconfiguration information before the activation command; or theactivation command includes a first part of the first configurationinformation, and the transmitter sends a second part of the firstconfiguration information before the activation command.

In an optional design, before the transmitter sends the first referencesignal to the terminal device according to the first configurationinformation,

-   -   when the processor determines that a difference between the        available second reference signal of the terminal device and a        current time exceeds a first threshold, the processor determines        that the first reference signal is sent to the terminal device,        where the first threshold is preset.

In an optional design, the access network device further includes areceiver, and the receiver is configured to receive the channelmeasurement result from the terminal device.

The second aspect further includes a communications apparatus, where thecommunications apparatus includes a receiver and a processor;

-   -   the receiver is configured to receive an activation command from        an access network device, where the activation command is used        to indicate activating a secondary cell;    -   the receiver is further configured to receive first        configuration information of a first reference signal from the        access network device;    -   the receiver is further configured to receive the first        reference signal according to the first configuration        information; and    -   the processor is configured to obtain a channel measurement        result of the secondary cell according to the first reference        signal.

In an optional design, the first reference signal is located before anavailable second reference signal of the communications apparatus intime domain, and the second reference signal is configured by usingsecond configuration information; or

-   -   the first reference signal is located between two adjacent        second reference signals of the communications apparatus in time        domain, and the two adjacent second reference signals are        configured by using same second configuration information.

In an optional design, the activation command includes the firstconfiguration information; or the receiver receives the firstconfiguration information before the activation command; or theactivation command includes a first part of the first configurationinformation, and the receiver receives a second part of the firstconfiguration information before the activation command.

In an optional design, the communications apparatus further includes atransmitter, and the transmitter is configured to send the channelmeasurement result to the access network device.

In the access network device and the communications apparatus providedin the second aspect, optional designs are as follows:

In an optional design, the second reference signal is periodic.

In an optional design, the first reference signal is a synchronizationsignal or a channel state information reference signal.

In an optional design, the first configuration information includes atleast one of the following information:

-   -   a reference signal sending indication;    -   a reference signal sending time;    -   a reference signal period;    -   a reference signal time domain resource location;    -   a reference signal frequency domain resource location; and    -   a reference signal configuration index, where the reference        signal configuration index is used to indicate a location of        reference signal configuration information.

The reference signal sending time of the first reference signal is arelative time difference between a time at which the access networkdevice (the transmitter of the access network device) sends the firstreference signal and a time at which the access network device (thetransmitter of the access network device) sends the activation command,or is a time at which the access network device (the transmitter of theaccess network device) sends the first reference signal.

According to a third aspect, the present invention provides a system,including the access network device and the communications apparatusprovided in the second aspect.

According to a fourth aspect, the present invention provides acommunications apparatus, where the communications apparatus includes aprocessor and a memory, the memory stores a computer program, and whenthe processor executes the computer program, the method in the foregoingaspect is implemented.

According to a fifth aspect, the present invention provides a computerstorage medium storing a computer program, where the computer storagemedium stores a computer program, and when the computer program isexecuted by a processor, the method in the foregoing aspect isimplemented.

According to a sixth aspect, the present invention provides a computerprogram product including an instruction, where when the computerprogram product is run on a computer, the computer is enabled to performthe method in the foregoing aspect.

According to a seventh aspect, the present invention provides a chipsystem, where the chip system includes a processor, configured tosupport the access network device or the communications apparatus inimplementing functions in the foregoing aspect, for example, generatingor processing data and/or information in the foregoing method. In apossible design, the chip system further includes a memory, and thememory is configured to store a program instruction and data that arenecessary for the access network device or the communications apparatus.The chip system may include a chip, or may include a chip and anotherdiscrete component.

The embodiments of the present invention provide the secondary cellactivation method, the access network device, the communicationsapparatus, and the communications system. According to the solutions ofthe embodiments of the present invention, the access network device maysend the first reference signal and the first configuration informationof the first reference signal to the terminal device, so that theterminal device performs channel measurement on the first referencesignal according to the first configuration information. This solutionavoids scenarios in which a secondary cell can be measured and activatedbased only on a fixedly configured reference signal, so as to improvesecondary cell activation flexibility, and improve secondary cellactivation efficiency.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly describes the accompanyingdrawings required for describing the embodiments. It is clearly that theaccompanying drawings in the following description show merely someembodiments of the present invention, and a person of ordinary skill inthe art may derive other drawings from these accompanying drawingswithout creative efforts.

FIG. 1 is a flowchart of a secondary cell activation method in aconventional LTE system;

FIG. 2 is a schematic structural diagram of a communications system 100according to an embodiment;

FIG. 3 is a flowchart of a secondary cell activation method according toan embodiment;

FIG. 4 is a schematic diagram of synchronization signal transmission ina scenario of a plurality of beams in an NR system;

FIG. 5 is a schematic diagram of an optional configuration of a firstreference signal in a secondary cell activation method according to anembodiment;

FIG. 6 is a schematic structural diagram of an access network deviceaccording to an embodiment;

FIG. 7 is a schematic structural diagram of another access networkdevice according to an embodiment;

FIG. 8 is a schematic structural diagram of a communications apparatusaccording to an embodiment; and

FIG. 9 is a schematic structural diagram of another communicationsapparatus according to an embodiment.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of thepresent invention clearer, the following further describes theimplementations of the present invention in detail with reference to theaccompanying drawings.

In a conventional secondary cell activation method, in response to anactivation command received from an access network device, a terminaldevice measures a reference signal and feeds back a measurement result.When a secondary cell is in an inactive state, the terminal device doesnot listen to a downlink control channel, does not send uplink data andchannel state information, or the like in the secondary cell. After thesecondary cell is activated, the terminal device starts correspondinglistening and transmission.

It should be noted herein that, in a secondary cell activation process,the access network device needs to obtain, from the terminal device,information related to a current downlink channel state, and theinformation is usually referred to as channel state information (CSI).In an LTE release 8, the CSI includes channel quality information (CQI),a precoding matrix indication (PMI), and a rank indication (RI). In asubsequent release, CSI in another form is further included, forexample, explicit channel quantization, effective channel quantizationincluding receiver processing, a noise plus interference feedback, and areceive covariance feedback. In the embodiments of the presentinvention, specific content included in the CSI is not limited. A CSIreport may be periodically reported by the terminal according toconfiguration information of the CSI, or may be fed back by the terminaldevice in response to a request of the access network device. Theterminal device may determine, according to a location at which therequest is received, a cell that needs to be measured, or addinformation used to identify the cell to the request of the accessnetwork device, so that the terminal device determines the cell thatneeds to be measured. To feed back a CSI measurement report, theterminal device needs to measure a downlink reference signal.

FIG. 1 shows a secondary cell activation method in a conventional LTEsystem. In the LTE system, one cell corresponds to one carrier, andtechnical processing in cell activation is the same as that in carrieractivation. A reference signal used for CSI measurement in the LTEsystem is a common reference signal CRS. When an access network deviceneeds to activate a secondary cell for a terminal device, the accessnetwork device sends a secondary cell activation command to the terminaldevice. In response to the activation command, the terminal deviceperforms channel measurement according to the reference signal, andfeeds back CSI. Before obtaining a valid CSI measurement value, theterminal device needs to first obtain initial synchronization accordingto a synchronization signal of the secondary cell, and then obtain finesynchronization according to a reference signal of the secondary cell,so as to perform CSI measurement and generate the CSI. When the terminaldevice receives a first secondary cell activation command in a subframeN, to make the access network device and the terminal device have a sameunderstanding, the terminal device starts to report the CSI of theto-be-activated secondary cell after a subframe N+8. For example, theterminal device needs to report the CSI in a subframe N+4 and a subframeN+10 according to a CSI reporting period. Therefore, a CSI report of afirst secondary cell is carried in the subframe N+10 instead of a CSIreport of the subframe N+4. However, for a secondary cell in adeactivated state, a time at which the terminal device can obtain validCSI may vary with a state in which the terminal device tracks thedeactivated secondary cell, for example, whether the terminal device issynchronized with the secondary cell, or whether the terminal devicemeasures the secondary cell within a specific time. If the terminaldevice is not synchronized with the secondary cell, or does not measurethe secondary cell within a specific time, the terminal device may notobtain a valid CSI measurement value when reporting the CSI in thesubframe N+10 after the subframe N+8 for the first time. In this case,the terminal device needs to fill a special measurement value into theCSI reported in the subframe N+10, to notify the access network devicethat the terminal device does not obtain the valid measurement value.The terminal device does not start to fill a normal CSI measurementvalue until the terminal device receives and measures a CRS in asynchronization state to obtain the valid CSI measurement value.However, the terminal device starts to report valid CSI in a subframethat is not later than a subframe N+24 (for example, the terminal devicehas recently measured the secondary cell, or the terminal device issynchronized with the secondary cell) or a subframe N+34 (for example,the terminal device has not recently measured the secondary cell, or theterminal device is not synchronized with the secondary cell). Forexample, if the terminal device has measured the secondary cell within atime before the terminal device receives the activation command, theterminal device needs to report the valid CSI before the subframe N+24.If the terminal device has not measured the secondary cell within a timebefore the terminal device receives the activation command, the terminaldevice needs to report a valid CSI before the subframe N+34.

It should be noted that, in the following embodiments of the presentinvention, a delay between the access network device and the terminaldevice is ignored, to ensure that a signal or information that aretransmitted between the access network device and the terminal devicetake effect at the same time.

The technology in the present invention may be applied to a long termevolution (LTE) system or other wireless communications systems usingvarious radio access technologies, for example, systems using accesstechnologies such as code division multiple access, frequency divisionmultiple access, time division multiple access, orthogonal frequencydivision multiple access, and single carrier frequency division multipleaccess. Particularly, the technology may be applied to a subsequentevolved system using the LTE system and a new radio (NR) system such asa fifth-generation (5G) system. The system includes an access networkdevice and a terminal device. The access network device includes atleast one cell, and provides a service for the terminal device by usingthe cell. In a system to which a carrier aggregation technology isapplied, a plurality of component carriers that all serve one terminaldevice include a primary component carrier and a secondary componentcarrier. Cells aggregated by the terminal device having a carrieraggregation function include one primary cell and several secondarycells. A cell corresponding to the primary component carrier is referredto as a primary cell, and a cell corresponding to the secondarycomponent carrier is referred to as a secondary cell. The primary cell(PCell) provides non-access stratum NAS) mobility information (forexample, a tracking area identity (TAI)) during radio resource control(RRC) connection establishment, re-establishment, or switching. Thesecondary cell (SCell) may be activated or deactivated by the accessnetwork device, and implements data transmission between the accessnetwork device and the terminal device when the secondary cell isactivated. It should be noted herein that the primary cell and thesecondary cell each may function differently in different systems. Withdevelopment of technologies, the primary cell and the secondary cell mayhave further meanings in the NR system. This is not specifically limitedherein.

The terminal device in the present invention is a device having wirelessreceiving and sending functions, and may be deployed on land, forexample, an indoor or outdoor device, a handheld device, or avehicle-mounted device, or may be deployed on water (for example, on asteamship), or may be deployed in the air (for example, on an airplane,a balloon, or a satellite). The terminal device may be a mobile phone, atablet computer (Pad), a computer having wireless receiving and sendingfunctions, a virtual reality (VR) terminal device, an augmented reality(AR) terminal device, an industrial control wireless terminal, a selfdriving wireless terminal, a remote medical wireless terminal, a smartgrid wireless terminal, a transportation safety wireless terminal, asmart city wireless terminal, a smart home wireless terminal, or thelike.

The access network device in the present invention is an apparatus thatis deployed in a radio access network and that is configured to providea wireless communication function for the terminal device, for example,a base station (BS). The base station may include various forms of macrobase stations, micro base stations, relay stations, access points, andthe like. A name of a base station having a base station function mayvary with a radio access technology used in a system. For example, in anLTE network, the base station is referred to as an evolved NodeB (i.e.,an evolved NodeB, eNB or eNodeB), in a third-generation 3G network, thebase station is referred to as a NodeB or the like, and in a subsequentevolved system, the base station may be referred to as a gNB. It shouldbe noted that, in the 5G or NR system, one NR gNB may include one ormore transmission reception points (TRP). All TRPs belong to a samecell, and both each TRP and the terminal can use a measurement reportingmethod described in the embodiments of the present invention. In anotherscenario, the network device 12 may further include a control unit (CU)and a data unit (DU). One CU may correspond to a plurality of DUs, andboth each DU and the terminal can use the measurement reporting methoddescribed in the embodiments of the present invention. A differencebetween a CU-DU separation scenario and a multi-TRP scenario lies inthat the TRP is merely a radio frequency unit or an antenna device whilethe DU can implement a protocol stack function. For example, the DU canimplement a physical layer function.

For ease of description, in this application, the access network deviceand the terminal device are used as examples to describe theembodiments.

FIG. 2 is a schematic structural diagram of a communications system 100according to an embodiment. The communications system includes an accessnetwork device and terminal devices 1 and 2. Serving cells of theterminal device 1 and the terminal device 2 are from a same accessnetwork device. In a communications system to which a carrieraggregation technology is applied, a plurality of component carriersthat all serve one terminal device include a primary component carrierand a secondary component carrier. Cells aggregated by the terminaldevice having a carrier aggregation function include one primary celland several secondary cells. A cell corresponding to the primarycomponent carrier is referred to as a primary cell, and a cellcorresponding to the secondary component carrier is referred to as asecondary cell. The primary cell (PCell) is a cell determined duringinitial access of the terminal device. The terminal device establishes aradio resource control connection in the primary cell, and performsinitial call establishment, radio resource control (RRC)reconfiguration, cell handover, and the like in the primary cell. Thesecondary cell (SCell) is added during RRC reconfiguration, and isconfigured to provide an additional radio resource and perform datatransmission. The access network device may activate or deactivate thesecondary cell according to a requirement. When the secondary cell is inan inactive state, the terminal device does not listen to a downlinkcontrol channel, does not send uplink data and channel stateinformation, or the like in the secondary cell. After the secondary cellis activated, the terminal device starts corresponding listening andtransmission. In FIG. 1, the terminal device 1 and the terminal device 2are separately connected to a plurality of carriers of the accessnetwork device. A serving cell of the terminal device 2 includes aprimary cell and two secondary cells (a secondary cell 1 and a secondarycell 2). A serving cell of the terminal device 1 includes the primarycell and the secondary cell 1.

When the secondary cell needs to be activated, the access network devicesends an activation command to the terminal device. In response to theactivation command received from the access network device, the terminaldevice measures a channel state and feeds back a measurement result ofthe channel state. To obtain channel state information, the terminaldevice needs to measure a downlink reference signal. In other words, ina secondary cell activation process, the access network device needs toobtain a measurement result of a downlink channel state from theterminal device, for example, the channel state information (CSI). In anLTE release 8, the CSI includes channel quality information (CQI), aprecoding matrix indication (Precoding Matrix Indication, PMI forshort), and a rank indication (Rank Indication, RI for short), and mayfurther include CSI in another form, for example, a noise plusinterference feedback and a receive covariance feedback. In thisembodiment of the present invention, specific content included in theCSI is not limited.

An example in which the communications system 100 is an NR system isused below for description. A reference signal used in the NR system inthis embodiment of the present invention may not include a CRS. Areference signal used for channel state measurement required bysecondary cell activation includes a synchronization signal or anadditional reference signal (ARS). The synchronization signal includes aprimary synchronization signal and a secondary synchronization signal. Asending period of the reference signal may be configured. In the NRsystem, the synchronization signal may further include a signal ofanother type. In this embodiment of the present invention, when thesynchronization signal is used to measure secondary cell activation, oneor more of a plurality of different signals included in thesynchronization signal may be measured. This is not specifically limitedherein.

The synchronization signal is a known sequence, and may be a sequencewith good autocorrelation and low cross-correlation, for example, aZadoff-Chu (ZC) sequence. The terminal device performs synchronizationcorrelation with the synchronization signal from the access networkdevice according to a local sequence, to implement synchronization withthe access network device. A difference between NR and a conventionalcommunications system lies in that a beamforming technology is used inthe NR system. In the beamforming technology, a propagation directionmay be controlled by using an analog beam and/or a digital beam, toobtain a significant gain. The NR system transmits a control channel ina beamforming transmission manner. A reference signal corresponding tothe control channel is also transmitted by using a same beam. To moreflexibly perform synchronization, a sending period of thesynchronization signal may be dynamically configured.

In a high-frequency multi-beam transmission scenario, one cellcorresponds to at least one beam. A synchronization signal of each cellincludes at least one synchronization signal block (SS block). Thecorresponding synchronization signal block is sent on the at least onebeam corresponding to the cell. To be specific, synchronization signalsof a plurality of cells are sent in a synchronization signal set period,and one period includes several synchronization signal bursts (SSburst), each synchronization signal burst corresponds to one cell, andeach synchronization signal burst includes at least one synchronizationsignal block. When activating a secondary cell, the access networkdevice needs to send the synchronization signal block on some or all ofthe at least one beam. The terminal device measures each synchronizationsignal block, feeds back a measurement result of each synchronizationsignal block, and reports CSI to the access network device.

In addition to the synchronization signal, the additional referencesignal may be further used to perform CSI measurement. The additionalreference signal may, for example, include a channel stateinformation-reference signal (CSI-RS). The additional reference signalmay be independently sent for the terminal device. Therefore, a sendingperiod or a sending frequency of the additional reference signal mayalso be configured, so as to more quickly and more accurately performmeasurement.

This embodiment provides a secondary cell activation method. The accessnetwork device may send a first reference signal and first configurationinformation of the first reference signal to the terminal device, sothat the terminal device performs channel measurement on the firstreference signal according to the first configuration information. Thisimproves secondary cell activation flexibility and efficiency.

It should be noted that the activation command may be used to indicateactivating one or more secondary cells. When the activation commandindicates activating a plurality of secondary cells, the access networkdevice activates the plurality of secondary cells in a same manner. Aprocedure of activating one secondary cell is used as an example belowfor description. A person skilled in the art may learn that, when theactivation command indicates activating a plurality of secondary cells,the secondary cell activation method in this embodiment of the presentinvention may be used for any one of the plurality of to-be-activatedsecondary cells.

The following further describes this embodiment of the present inventionin detail.

FIG. 3 is a flowchart of a secondary cell activation method according toan embodiment. The method specifically includes the following steps:

Step 301: An access network device sends an activation command to aterminal device, where the activation command is used to indicateactivating a secondary cell, and the terminal device at Step 302receives the activation command.

Step 303: The access network device sends first configurationinformation of a first reference signal to the terminal device, and theterminal device at Step 304 receives the first configurationinformation.

The first reference signal is used by the terminal device to performchannel measurement and generate a measurement result in response to theactivation command.

Step 305: The access network device sends the first reference signal tothe terminal device according to the first configuration information,where the first reference signal is used to obtain a channel measurementresult of the secondary cell.

Step 306: The terminal device measures the first reference signalaccording to the first configuration information, and obtains thechannel measurement result.

In steps 301 to 305, the access network device activates the secondarycell for the terminal device. Optionally, the method further includesstep 307: The terminal device sends the channel measurement result tothe access network device, and the access network device at Step 308receives the channel measurement result from the terminal device.Finally, after the access network device receives the measurementresult, the access network device and the terminal device may performdata or information transmission by using the secondary cell.

It should be noted herein that numbers of the foregoing steps do notlimit a sequence in a specific execution process. In different optionaldesigns, a sequence of performing the foregoing steps is adaptivelyadjusted.

According to the solution in this embodiment of the present invention,the access network device may send the first reference signal and thefirst configuration information of the first reference signal to theterminal device, so that the terminal device performs channelmeasurement on the first reference signal according to the firstconfiguration information. This solution avoids a scenario in which asecondary cell can be measured and activated based only on a CRS with afixed configuration or a fixed period, so as to improve secondary cellactivation flexibility, and improve secondary cell activationefficiency.

It should be noted herein that numbers of the foregoing steps do notlimit a sequence in a specific execution process. In different optionaldesigns, a sequence of performing the foregoing steps is adaptivelyadjusted.

In step 301 in this embodiment, the access network device may send theactivation command to the terminal device by using a primary cell or asecondary cell in an active state. The activation command may bephysical layer signaling or higher layer signaling, for example, mediaaccess control (MAC) signaling or RRC signaling. The activation commandmay include an indication used to activate and/or deactivate at leastone secondary cell, and may further include or indicate an identity ofan activated or deactivated secondary cell in another manner, forexample, a cell radio network temporary identifier (C-RNTI). In aspecific indication manner, different states of a bit may be used torepresent activation and deactivation. A format, a type, and anindication manner of the activation command are not specifically limitedherein.

For example, a format of the MAC layer signaling for activating and/ordeactivating the secondary cell may be as follows:

C₇ C₆ C₅ C₄ C₃ C₂ C₁ R

The MAC signaling includes indicator bits C₁ to C₇ and one reserved bitR, and each indicator bit may be 1-bit. The indicator bits C₁ to C₇correspond to seven secondary cells. For example, the seven secondarycells sequentially correspond to C₁ to C₇ in ascending order of cellidentities. If a value of any of the indicator bits C₁ to C₇ is 1, itindicates that a secondary cell corresponding to the indicator bit isactivated. If a value of the indicator bit is 0, it indicates that thesecondary cell corresponding to the indicator bit is deactivated.

Optionally, before sending the activation command, the access networkdevice determines whether the secondary cell needs to be activated forthe terminal device, for example, whether a relatively large amount ofdata needs to be transmitted between the access network device and theterminal device, or whether a primary cell and a current secondary cellin an active state cannot meet a transmission requirement. For example,the access network device learns, through statistics collection, that anamount of data transmitted between the access network device and theterminal device within a time exceeds a specific threshold, and thecurrent secondary cell cannot meet a transmission requirement.Alternatively, the access network may further receive feedbackinformation from the terminal device. The feedback information is usedto request the access network device to activate the secondary cell. Forexample, the terminal device determines that a service poses arelatively high requirement on a carrier resource or a networkbandwidth. When the requirement meets a specific threshold, the terminaldevice sends the feedback information to the access network device. Thefeedback information may be an activation request. For a specificdetermining manner, refer to the prior approaches or another case inwhich the secondary cell may need to be activated. This is notspecifically limited herein.

Optionally, the access network device may determine a quantity ofsecondary cells that need to be activated and the correspondingsecondary cells voluntarily or according to a rule. For example, theaccess network device determines, according to a maintained load statusof each secondary cell, one or more secondary cells with relativelylight historical load as a secondary cell to be activated currently. Foranother example, the access network device randomly selects one or moresecondary cells in a deactivated state. For still another example, theaccess network device determines a quantity of secondary cells that needto be activated and the corresponding secondary cells according to arule. The rule is preconfigured by the access network device, or ispre-agreed on between the access network device and the terminal device,or is specified in a protocol or a standard. The access network devicemay further determine, according to an amount of data transmittedbetween the access network device and the terminal device, a quantity ofsecondary cells that need to be activated. This is not specificallylimited herein.

In step 303 in this embodiment, the first reference signal may be anyreference signal that can be used by the terminal device to performchannel measurement. The following first and second implementations inthis embodiment separately describe a possible configuration manner ofthe first reference signal during specific implementation.

In the first implementation, the first reference signal is a referencesignal having a configurable period. In a communications system, it isconsidered by default or it is specified that the reference signal isused by the terminal device to perform channel measurement in responseto secondary cell activation command. In this implementation, inresponse to the activation instruction, the terminal device waits toreceive and measure a downlink reference signal according to theconfiguration information of the first reference signal. This overcomesa disadvantage that a secondary cell can be measured only by using aCRS, and improves secondary cell activation flexibility.

Specifically, the first reference signal may be a synchronization signalSS or an additional reference signal (ARS). The access network devicemay send the first configuration information of the first referencesignal to the terminal device in any one of a plurality of notificationmanners, for example, radio resource control (RRC) signaling, broadcastinformation, MAC signaling, or physical layer signaling. The additionalreference signal may be specifically a CSI-RS or a mobility referencesignal (MRS). The first configuration information includes at least oneof the following information: a reference signal sending indication, areference signal sending time, a reference signal period, a referencesignal time domain resource location, a reference signal frequencydomain resource location, and a reference signal configuration index.The reference signal configuration index is used to indicate a locationof reference signal configuration information. Optionally, the sendingtime of the first reference signal is a time difference between a timeat which the access network device sends the first reference signal anda time at which the access network device sends the activation command,or is a time at which the access network device sends the firstreference signal.

In an implementation, the first reference signal is a synchronizationsignal. Regardless of whether the terminal device is synchronized withthe to-be-activated secondary cell, the terminal device may activate thesecondary cell by using the first reference signal. Specifically, if theterminal device is not synchronized with the to-be-activated secondarycell, the terminal device receives the synchronization signal to performsynchronization and measurement. If the terminal device is synchronizedwith the to-be-activated secondary cell, the terminal device measuresthe synchronization signal to obtain the channel measurement result.

In another implementation, the first reference signal is an additionalreference signal such as a CSI-RS.

It should be noted that, in this implementation, the first referencesignal is configured by the access network device by using the firstconfiguration information, before the access network device sends theactivation command, and does not change with a scenario of sending theactivation command or a scenario of activating the secondary cell.Therefore, in this implementation, configuration information of thefirst reference signal may be referred to as the first configurationinformation. However, a meaning of the first configuration informationis different from that of “first configuration information” when thereis further “third configuration information” in the subsequent secondimplementation.

As described above, in an NR system in this embodiment, to more flexiblyperform synchronization, a sending period of the synchronization signalmay be dynamically configured. Although the synchronization signal issent periodically, the period may be relatively long or relativelyshort. In this scenario in which the period of the synchronizationsignal is dynamically configured, when the access network device needsto activate the secondary cell for the terminal device, if the accessnetwork device currently configures a relatively long period of thesynchronization signal, the terminal device needs to wait a relativelylong time before performing measurement. The following provides aspecific description with reference to FIG. 4. FIG. 4 is a schematicdiagram of synchronization signal transmission in a scenario of aplurality of beams in an NR system. During multi-beam transmission, thesecondary cell may interact with the terminal device on a plurality ofbeams. When sending the synchronization signal, the access networkdevice needs to separately send a corresponding synchronization signalblock on some or all of the plurality of beams corresponding to thesecondary cell, to form a synchronization signal burst. In onesynchronization signal period, if a synchronization signal burst(corresponding to a black beam) corresponding to the to-be-activatedsecondary cell just ends when the terminal device receives theactivation command for the to-be-activated secondary cell, the terminaldevice needs to wait for a synchronization signal burst (correspondingto a black beam) in a next synchronization signal period. Consequently,a relatively great delay is caused in a secondary cell activationprocess, especially when the synchronization signal period is relativelylong.

To resolve the foregoing problem, this embodiment further provides thefollowing second implementation. In the second implementation, the firstreference signal is temporarily configured or temporarily sent by theaccess network device, so that the terminal device responds to thesecondary cell activation command.

In a first optional design of the second implementation, the firstreference signal is located before an available second reference signalof the terminal device in time domain, and the second reference signalis configured by using second configuration information. The secondreference signal may be a reference signal that is the same as the firstreference signal. For example, both the first reference signal and thesecond reference signal are synchronization signals. The secondreference signal may alternatively be a reference signal that isdifferent from the first reference signal. For example, the firstreference signal is a synchronization signal, and the second referencesignal is an additional reference signal.

Specifically, an example in which both the first reference signal andthe second reference signal are synchronization signals is used fordescription. When the access network device determines that a period ofthe second reference signal that is currently configured forsynchronization is relatively long, and the terminal device needs towait a relatively long time before receiving the available secondreference signal in a secondary cell activation process, the accessnetwork device may send the first configuration information to theterminal device to configure the first reference signal with arelatively short period, to activate the secondary cell. After sendingthe first synchronization signal, the access network device may send thesecond configuration information to restore an original periodconfiguration of the second synchronization signal, or reconfigure theperiod of the second synchronization signal.

In a second optional design of the second implementation, the firstreference signal is located between two adjacent second referencesignals of the terminal device in time domain, and the two adjacentsecond reference signals are configured by using same secondconfiguration information. The second reference signal may be areference signal that is the same as the first reference signal. Forexample, both the first reference signal and the second reference signalare synchronization signals. The second reference signal mayalternatively be a reference signal that is different from the firstreference signal. For example, the first reference signal is asynchronization signal, and the second reference signal is an additionalreference signal.

For example, the access network device configures the second referencesignal having a specific period by using the second configurationinformation. When the access network device determines that the periodof the second reference signal that is currently configured forsynchronization is relatively long, and the terminal device needs towait a relatively long time before receiving the available secondreference signal in a secondary cell activation process, the accessnetwork device may temporarily insert the first reference signal betweenthe two adjacent second reference signals. In this way, the accessnetwork device does not need to reconfigure the second reference signal,but only needs to configure the first reference signal by using thefirst configuration information.

In the second optional design, the configuration of the first referencesignal is different from a configuration of an existing reference signalof a same type, and the first reference signal is temporarily sent toactivate the secondary cell. To distinguish between the configuration ofthe first reference signal and the configuration of the existingreference signal of a same type, herein, the configuration informationof the temporarily sent first reference signal is referred to as thefirst configuration information, a reference signal that has a same typeas the first reference signal and that has been preconfigured ordynamically configured before the first reference signal is referred toas a third reference signal, and configuration information of the thirdreference signal is referred to as third configuration information. Inthe NR system, there may be some reference signals that areaperiodically configured. Therefore, whether the third reference signalis a periodically or aperiodically configured reference signal is notlimited in this embodiment of the present invention. The firstconfiguration information is determined when the access network devicedetermines, when the secondary cell is activated, that there is aresource that can be used to temporarily send the first reference signalused to activate the secondary cell, and may be specifically sent to theterminal device by using higher layer signaling or physical layersignaling. This is not specifically limited herein. For ease ofdescription, the following provides a description by using a CSI-RS asan example for a case in which the first reference signal is anadditional reference signal.

It should be noted herein that the second reference signal is areference signal that is specified in the communications system and thatis used to perform channel measurement in response to the secondary cellactivation command, or is a reference signal that has a function ofperforming channel measurement in response to the secondary cellactivation command. In addition, the second reference signal is alsoconfigured for measurement (for example, the synchronization signal isconfigured for synchronization). Configuration information of the secondreference signal is referred to as the second configuration information.The second configuration information is semi-statically or dynamicallyconfigured by the access network device, or is specified in a protocolor a standard, or is negotiated by the access network device and theterminal device, or is determined in another manner to activate thesecondary cell. The second configuration information does not changewith a scenario of activating the secondary cell. The first referencesignal is a reference signal that is temporarily sent to perform channelmeasurement when the secondary cell is activated, and the configurationinformation of the first reference signal is referred to as the firstconfiguration information. The first reference signal and the secondreference signal may be reference signals of a same type, or may bereference signals of different types.

In the second implementation, before step 303, optionally, the accessnetwork device needs to determine whether to send the first referencesignal to the terminal device. Specifically, FIG. 5 is a schematicdiagram of an optional configuration of the first reference signal in asecondary cell activation method.

In FIG. 5, the access network device determines to activate thesecondary cell for the terminal device, and sends the activation commandat a moment t1. The access network device determines, according to thesecond configuration information, that a moment t0 and a moment t2 areadjacent moments at which the access network device delivers the secondreference signal according to the second configuration information. Themoment t0 is before the moment t1, and the moment t2 is after the momentt1. In this case, the terminal device needs to wait first duration tafter receiving the activation command, to receive and measure acorresponding reference signal, where t=t2−t1. If a period of thereference signal is relatively long, or the activation command needs tobe delivered after the moment t0 just passes, the terminal device needsto wait a very long time before measuring the corresponding secondreference signal at the moment t2.

In this scenario, to reduce a delay generated when the secondary cell isactivated and improve secondary cell activation efficiency, the accessnetwork device may temporarily send a group of first reference signalsat a moment t3 between the moment t1 and the moment t2, so that theterminal device can quickly detect a reference signal and feed back ameasurement result in response to the activation command. Thetemporarily sent reference signal is sent according to the firstconfiguration information, and the first configuration information needsto be notified to the terminal device before the temporarily sentreference signal is sent. Content and a sending manner of the firstconfiguration information are described in detail below. Optionally, theaccess network device determines a first threshold, so that the accessnetwork device determines to temporarily send a group of referencesignals for secondary cell activation when the first duration t isgreater than the first threshold. Optionally, the first threshold may bedetermined by the access network device voluntarily, or may be specifiedin a standard or a protocol, or may be negotiated by the access networkdevice and the terminal device. This is not specifically limited herein.

Specifically, when the first reference signal needs to be sent, to sendthe first reference signal, the access network device further needs todetermine an available resource to send the first reference signal, anddetermine the first configuration information according to the availableresource.

The following further describes the second implementation by usingexamples.

Example 1

The first reference signal is a synchronization signal SS, and the firstconfiguration information in step 303 is configuration information of asynchronization signal SS that is temporarily sent to activate thesecondary cell.

In an optional design, an example in which the second reference signalis a synchronization signal is used. In an existing LTE system, a periodof the synchronization signal SS is fixed, for example, 5 ms. In the NRsystem, a period of the synchronization signal may be dynamicallyconfigured, and periods may differ greatly in duration. To improvesecondary cell activation efficiency, the access network device maytemporarily send the SS, so that the terminal device measures thesecondary cell.

With reference to the foregoing description of this embodiment of thepresent invention, if the access network device determines that a groupof synchronization signals need to be temporarily sent, the accessnetwork device needs to determine whether there is an available resourcethat is used to send the synchronization signal. If there is anavailable resource, the access network device determines the firstconfiguration information. If there is no available resource, the accessnetwork device cannot temporarily send the synchronization signal, andthe terminal device may wait to receive and measure a synchronizationsignal at a next moment according to the activation command and thesecond configuration information.

If the access network device determines that there is a resource thatcan be used to temporarily send the first reference signal, namely, thesynchronization signal, the access network device sends the firstconfiguration information of the resource for temporarily sending thesynchronization signal and the synchronization signal to the terminaldevice. The group of temporarily sent synchronization signals may besent periodically, or may be sent once. This is not specifically limitedherein. However, the first configuration information of the temporarilyinserted synchronization signal needs to be sent to the terminal device,so that the terminal device receives and measures the synchronizationsignal. Specifically, the first reference signal is located before anavailable second reference signal of the terminal device in time domain,and the available second reference signal is configured by using secondconfiguration information. Optionally, in time domain, the firstreference signal is located between two second reference signals thatare adjacent in time domain and that are configured by using the secondconfiguration information.

In this optional design, in response to the secondary cell activationcommand, before sending a next second reference signal in time domainthat can be used to perform channel measurement when the secondary cellis activated, the access network device may pre-configure the firstreference signal by using the first configuration information, and sendthe first reference signal to the terminal device, so that the terminaldevice does not need to wait a relatively long time before receiving theforegoing available second reference signal, but quickly receives thefirst reference signal to perform channel measurement, and obtains thechannel measurement result. This improves secondary cell activationefficiency.

In this optional design, the first reference signal and the secondreference signal are reference signals of a same type, and aredistributed at different locations in time domain. Sending of the firstreference signal is configured by using the first configurationinformation, and is used to activate the secondary cell. Sending of thesecond reference signal is configured by using the second configurationinformation, and is used to implement synchronization with the terminaldevice. Optionally, the second reference signal is sent periodically,and a plurality of second reference signals are distributed at differenttime domain locations. This is not specifically limited herein.

In another optional design, the second reference signal may be areference signal of another type other than a synchronization signal,for example, an additional reference signal. Herein, a CSI-RS is used asan example for description.

With reference to the foregoing description of this embodiment of thepresent invention, if the access network device determines that a groupof synchronization signals need to be temporarily sent, the accessnetwork device needs to determine whether there is an available resourcethat is used to send the synchronization signal. If there is anavailable resource, the access network device determines the firstconfiguration information. If there is no available resource, the accessnetwork device cannot temporarily send the synchronization signal, andthe terminal device may wait to receive and measure a next availablesecond reference signal according to the activation command and thesecond configuration information of the second reference signal CSI-RSthat is specified in the communications system and that is used toactivate the secondary cell.

If the access network device determines that there is a resource thatcan be used to temporarily send the first reference signal, namely, thesynchronization signal, the access network device delivers the firstconfiguration information of the resource for temporarily sending thesynchronization signal and the synchronization signal to the terminaldevice. The group of temporarily sent synchronization signals may besent periodically, or may be sent once. This is not specifically limitedherein. However, the first configuration information of the temporarilyinserted synchronization signal needs to be sent to the terminal device,so that the terminal device receives and measures the synchronizationsignal. Specifically, the first reference signal is located before anavailable second reference signal of the terminal device in time domain,and the available second reference signal is configured by using secondconfiguration information. Optionally, in time domain, the firstreference signal is located between two second reference signals thatare adjacent in time domain and that are configured by using the secondconfiguration information.

In this optional design, the first reference signal and the secondreference signal are reference signals of different types, and aredistributed at different locations in time domain. Sending of the firstreference signal is configured by using the first configurationinformation, and is temporarily sent to activate the secondary cell.Sending of the second reference signal is configured by using the secondconfiguration information, and is used to perform specific measurement.For example, the CSI-RS is used to measure data scheduling, and send areference signal before data on an antenna port to perform measurement.For another example, the MRS is used to measure mobility of the terminaldevice. Optionally, the second reference signal is sent periodically,and a plurality of second reference signals are distributed at differenttime domain locations. This is not specifically limited herein.

In the example 1, the access network device does not need to considerwhether the terminal device is synchronized with the secondary cell, buttemporarily sends a group of synchronization signals when there is anavailable resource, so that the terminal device performs channelmeasurement. In this way, the terminal device is prevented from waitinga very long time, and secondary cell activation flexibility andefficiency are improved.

Example 2

The first reference signal is an additional reference signal such as aCSI-RS or an MRS, and the first configuration information in step 303 isconfiguration information of the additional reference signal. Similar tothe first implementation, if the access network device determines that agroup of additional reference signals need to be temporarily sent, theaccess network device needs to determine whether there is an availableresource that is used to send the additional reference signal. If thereis an available resource, the access network device determines the firstconfiguration information. If there is no available resource, the accessnetwork device cannot temporarily send the additional reference signal,and the terminal device may wait to receive and measure an additionalreference signal at a next moment according to the activation commandand the second configuration information.

In an optional design, an example in which the second reference signalis an additional reference signal is used. The second reference signaland the first reference signal have a same type, for example, both areCSI-RSs. With reference to the foregoing description of this embodimentof the present invention, if the access network device determines that agroup of first reference signals need to be temporarily sent, the accessnetwork device needs to determine whether there is an available resourcethat is used to send the first reference signal. If there is anavailable resource, the access network device determines the firstconfiguration information. If there is no available resource, the accessnetwork device cannot temporarily send the first reference signal, andthe terminal device may wait to receive and measure a second referencesignal at a next moment according to the activation command and thesecond configuration information.

If the access network device determines that there is a resource thatcan be used to temporarily send the first reference signal, namely, theadditional reference signal, the access network device delivers thefirst configuration information of the resource for temporarily sendingthe additional reference signal and the additional reference signal tothe terminal device. The group of temporarily sent additional referencesignals may be sent periodically, or may be sent once. This is notspecifically limited herein. However, the first configurationinformation of the temporarily inserted additional reference signalneeds to be sent to the terminal device, so that the terminal devicereceives and measures the additional reference signal. Specifically, thefirst reference signal is located before an available second referencesignal of the terminal device in time domain, and the available secondreference signal is configured by using second configurationinformation. Optionally, in time domain, the first reference signal islocated between two second reference signals that are adjacent in timedomain and that are configured by using the second configurationinformation.

In this optional design, the first reference signal and the secondreference signal are additional reference signals of a same type, andare distributed at different locations in time domain. Sending of thefirst reference signal is configured by using the first configurationinformation, and is temporarily sent to activate the secondary cell.Sending of the second reference signal is configured by using the secondconfiguration information, and is used to perform specific measurement.For example, the CSI-RS is used to measure data scheduling, and send areference signal before data on an antenna port to perform measurement.Optionally, the second reference signal is sent periodically, and aplurality of second reference signals are distributed at different timedomain locations. This is not specifically limited herein.

In another optional design, the second reference signal is a referencesignal the type of which is different from the first reference signal.For example, the second reference signal is a synchronization signal,and the first reference signal is a CSI-RS.

With reference to the foregoing description of this embodiment, toactivate the secondary cell, if the access network device determinesthat a group of CSI-RSs need to be temporarily sent, the access networkdevice needs to determine whether there is an available resource that isused to send the CSI-RS. If there is an available resource, the accessnetwork device determines the first configuration information. If thereis no available resource, the access network device cannot temporarilysend the CSI-RS, and the terminal device may wait to receive and measurea next available second reference signal according to the activationcommand and the second configuration information of the second referencesignal that is specified in the communications system and that is usedto activate the secondary cell.

If the access network device determines that there is a resource thatcan be used to temporarily send the first reference signal, namely, theCSI-RS, the access network device delivers the first configurationinformation of the resource for temporarily sending the CSI-RS and theCSI-RS to the terminal device. The group of temporarily sent CSI-RSs maybe sent periodically, or may be sent once. This is not specificallylimited herein. However, the first configuration information of thetemporarily inserted CSI-RS needs to be sent to the terminal device, sothat the terminal device receives and measures the CSI-RS. Specifically,the first reference signal is located before an available secondreference signal of the terminal device in time domain, and theavailable second reference signal is configured by using secondconfiguration information. Optionally, in time domain, the firstreference signal is located after a second reference signal that islocated prior to the available second reference signal in time domainand that is configured by using the second configuration information.

In the example 2, the first reference signal and the second referencesignal are reference signals of different types, and are distributed atdifferent locations in time domain. Sending of the first referencesignal is configured by using the first configuration information, andis temporarily sent to activate the secondary cell. Sending of thesecond reference signal is configured by using the second configurationinformation, and is used to implement synchronization between theterminal device and the cell. Optionally, the second reference signal issent periodically, and a plurality of second reference signals aredistributed at different time domain locations. This is not specificallylimited herein.

It should be noted herein that, when it is considered by default or itis specified in the communications system that a synchronization signalis used to activate a secondary cell, the terminal device receives andmeasures the synchronization signal sent by the access network device,and feeds back the measurement result to the access network device.According to the foregoing description, the synchronization signaloccupies more resources than the additional reference signal such as theCSI-RS, especially when the secondary cell corresponds to a plurality ofbeams, and a synchronization signal block needs to be sent on at leastone of the plurality of beams to complete synchronization or secondarycell activation. To improve secondary cell activation efficiency, whendetermining that the synchronization signal needs to be temporarily sentto activate the secondary cell, the access network device may obtain,only after a very long time, sufficient resources used to temporarilysend the synchronization signal, or cannot obtain, before a nextavailable second reference signal configured by using the secondconfiguration information is sent, sufficient resources used totemporarily send the synchronization signal. In this way, secondary cellactivation efficiency cannot be improved. Therefore, in this optionaldesign, because the additional reference signals such as the CSI-RS isof relatively sparse distribution on a resource, and occupies arelatively small quantity of resources, the access network device easilyobtains an available resource used to temporarily send the firstreference signal, so that the secondary cell can be quickly measured andactivated.

Therefore, in the example 2, the first reference signal is theadditional reference signal such as either of the CSI-RS and the MRS.The access network device may temporarily send, according to arequirement for activating the secondary cell, a group of firstreference signals that are used to easily obtain a sending resource, toactivate the secondary cell, so that secondary cell activationefficiency and flexibility are improved.

It should be noted herein that, in a scenario in which the additionalreference signal is used to measure and activate the secondary cell, theterminal device needs to be synchronized with the secondary cell. Inthis case, before sending the additional reference signal, the accessnetwork device needs to determine a synchronization status. Ifdetermining that the terminal device is not synchronized with thesecondary cell, the access network device can send the additionalreference signal only after the terminal device is synchronized with thesecondary cell, to subsequently activate and measure the secondary cell.For a manner of synchronization with the secondary cell, refer toimplementation in prior approaches. A specific manner of activating thesecondary cell by using the additional reference signal is similar to amanner of activating the secondary cell by using the synchronizationsignal. For details, refer to the descriptions of the foregoingimplementations.

Example 3

Before step 303, an optional step may further be included: The accessnetwork device determines whether the terminal device is synchronizedwith the secondary cell.

If the access network device determines that the terminal device is notsynchronized with the secondary cell, the first reference signal is asynchronization signal; or if the access network device determines thatthe terminal device is synchronized with the secondary cell, the firstreference signal is either of an additional reference signal and asynchronization signal, or both an additional reference signal and asynchronization signal may be used as the first reference signal.

With reference to the foregoing description of the second implementationof this embodiment, if the access network device determines that a groupof first reference signals need to be temporarily sent, the accessnetwork device determines, according to the foregoing determiningresult, a type of the first reference signal (a synchronization signalor an additional reference signal) that needs to be sent, and then theaccess network device determines whether there is an available resourcethat is used to send the first reference signal whose type isdetermined. If there is an available resource, the access network devicedetermines the first configuration information. If there is no availableresource, the access network device cannot temporarily send the firstreference signal, and the terminal device may wait to receive andmeasure a next available second reference signal according to theactivation command and the second configuration information.

If the access network device determines that there is a resource thatcan be used to temporarily send the first reference signal, the accessnetwork device delivers the first configuration information of theresource for temporarily sending the first reference signal and thefirst reference signal to the terminal device. The group of temporarilysent first reference signals may be sent periodically, or may be sentonce. This is not specifically limited herein. However, the firstconfiguration information of the temporarily inserted first referencesignal needs to be sent to the terminal device, so that the terminaldevice receives and measures the first reference signal. Specifically,the first reference signal is located before an available secondreference signal of the terminal device in time domain, and the secondreference signal is configured by using second configurationinformation. Optionally, in time domain, the first reference signal islocated between two second reference signals that are adjacent in timedomain and that are configured by using the second configurationinformation.

Optionally, in step 307, the terminal device determines, according towhether the terminal device is synchronized with the secondary cell,whether the terminal device needs to detect a synchronization signal oran additional reference signal, and measures a corresponding referencesignal according to the received first configuration information. Itshould be noted herein that the access network device and the terminaldevice determine, in a same manner, whether the terminal device issynchronized with the secondary cell. This determining manner may bepre-specified in a standard or a protocol, or may be negotiated by theaccess network device and the terminal device in advance, or may benotified by the access network device to the terminal device in advance.For example, the terminal device reports a valid measurement report oncewithin a specified time, to activate the secondary cell. This is notspecifically limited herein.

According to the description of the example 3, the access network devicefirst determines a synchronization status of the terminal device, anddetermines, according to the synchronization status, a specificreference signal that is to be used to activate the secondary cell. Thisimproves secondary cell activation flexibility and efficiency overall.

It should be noted that, in the second implementation, there is ascenario in which the terminal device cannot detect the first referencesignal according to the first configuration information, for example,because of channel interference. In this case, in response to theactivation command, the terminal device receives and measures, accordingto the second configuration information, a reference signal that iscommonly configured and that is used to activate the secondary cell, andfeeds back a measurement result to the access network device.Optionally, the measurement result may further include indicationinformation. The indication information is used to indicate that theterminal device does not detect the first reference signal, butmeasures, according to the second configuration information, thereference signal used to activate the secondary cell, and obtains themeasurement result. The access network device may determine subsequentprocessing according to the indication information, for example,activate another secondary cell. This is not limited herein.

Further, in the second implementation of this embodiment, in step 302,the first configuration information and the activation command may beseparately sent to the terminal device, or may be sent to the terminaldevice together. Alternatively, the first configuration informationincludes a first part and a second part, and the access network deviceseparately sends the first part and the second part to the terminaldevice.

In a first implementation, step 303 is performed before step 301. Thefirst configuration information is sent by the access network device tothe terminal device, for example, by using RRC configurationinformation. Step 303 is first performed: The terminal device firstreceives the first configuration information. Then, step 301 isperformed: The access network device sends the activation command. Inother words, before receiving the activation command, the terminaldevice obtains the configuration information of the reference signalused to activate the secondary cell. In this way, a design of theactivation command can be simplified, or even a format of the activationcommand in prior techniques does not need to be changed, so that afterreceiving the activation command, the terminal device measures the firstreference signal in time according to the first configurationinformation.

In this implementation, a sending time of the first configurationinformation may be statically or dynamically configured by the accessnetwork device, and a specific configuration manner is not specificallylimited. The following describes several possible implementations.

In a first optional design, when configuring the secondary cell for theterminal device, the access network device configures, for the terminaldevice, the first configuration information of the first referencesignal that is corresponding to the secondary cell and that is used toactivate the secondary cell. When determining that the access networkdevice sends the first reference signal, the terminal device receivesand measures the first reference signal according to the firstconfiguration information. Optionally, the first configurationinformation may be periodically or aperiodically sent by the accessnetwork device to the terminal device.

In a second optional design, the access network device sends the firstconfiguration information to the terminal device within a preset timebefore the access network device sends the activation command. Forexample, if the access network device determines that a secondary cellneeds to be activated for the terminal device, and determines that agroup of first reference signals need to be temporarily sent, the accessnetwork device sends the first configuration information within a presettime before the access network device determines to send the activationcommand or before a preset time before the access network device sendsthe activation command.

Optionally, the preset time may be preconfigured by the access networkdevice and notified to the terminal device, or may be pre-specified in aprotocol or standard. Specifically, after receiving the firstconfiguration information, the terminal device may determine to receive,within the preset time or after the preset time, the activation commandsent by the access network device, and receive and measure, according tothe first configuration information, the first reference signal afterreceiving the activation command.

In a third optional design, the access network device sends the firstconfiguration information to the terminal device before the activationcommand. The first configuration information may be periodic oraperiodic, or may be sent once. The terminal device receives andmeasures, according to latest first configuration information receivedbefore the activation command, the first reference signal afterreceiving the activation command. In this implementation, how long thefirst configuration information is sent to the terminal device inadvance is not limited. Before the activation command used to activatethe secondary cell is sent, the terminal device needs to obtain thefirst configuration information to measure the first reference signal.

In this implementation, optionally, the access network device furthersends reference signal indication information when sending theactivation command. The indication information is used to indicatesending of the first reference signal, to notify the terminal devicethat the access network device is to deliver the first reference signal.The terminal device may determine, according to the indicationinformation, that the access network device temporarily sends a group offirst reference signals, and receive and measure the first referencesignal according to the first configuration information. Optionally, theactivation command does not need to carry the reference signalindication information, and the activation command is used to indicatethat the access network device determines to send the first referencesignal. After receiving the activation command, the terminal devicereceives and measures the first reference signal according to the firstconfiguration information.

In a second implementation, steps 301 and 303 are performed at the sametime: The access network device sends the activation command and thefirst configuration information to the terminal device at the same time.Herein, “at the same time” means that the first configurationinformation is included in the activation command, or the firstconfiguration information and the activation command are included in onetransport block and delivered to the terminal device as a whole. Thetransport block herein may be a minimum unit used by the terminal deviceto perform modulation and demodulation. Alternatively, the configurationinformation and the activation command are sent to the terminal devicein different control units at the same time. The control unit herein maybe a MAC control element (CE), or may be a physical downlink controlchannel (PDCCH) command. Alternatively, the control unit may beimplemented in another manner. This is not specifically limited herein.

In a third implementation, step 303 is performed after step 301. Step301 is first performed: The access network device sends the activationcommand to the terminal device. Then, step 303 is performed: The accessnetwork device sends the configuration information of the firstreference signal to the terminal device. The terminal device receivesthe first configuration information after the activation command, andreceives and measures the first reference signal according to the firstconfiguration information. For a subsequent specific processing manner,refer to the foregoing description. Details are not described hereinagain.

Optionally, a time interval between a sending time of the activationcommand and a sending time of the first configuration information is T,and T may be fixed duration or non-fixed duration.

In a fourth implementation, the first configuration information mayinclude a first part and a second part, and the access network deviceseparately sends the first part and the second part to the terminaldevice by using first signaling and second signaling.

For example, the first part is sent to the terminal device by using thefirst signaling, and the second part is sent to the terminal device byusing the second signaling. A type of the first signaling is differentfrom that of the second signaling. Optionally, sending times of thefirst signaling and the second signaling may be the same or different.In addition, optionally, the first signaling or the second signaling maybe one of MAC signaling, RRC signaling, or physical layer signaling, ormay be signaling of another type.

For another example, the first part is sent to the terminal device byusing the first signaling, and the second part is sent to the UE byusing the second signaling. The first signaling and the second signalinghave a same type but different sending times. Specifically, the firstpart and the activation command may be sent at the same time, and thesecond part may be sent before or after the activation command. Herein,“at the same time” may be that the first part is included in theactivation command, or the first part and the activation command areincluded in one transport block and delivered to the terminal device asa whole. Alternatively, the first part and the activation command aresent to the terminal device in different control units at the same time.Alternatively, the control unit may be implemented in another manner.This is not specifically limited herein. For explanations of thetransport block and the control unit, refer to the foregoingdescription.

Further, in the second implementation of this embodiment, the firstconfiguration information may include one or more of a reference signalsending indication, a reference signal sending time, a reference signalperiod, a reference signal time domain resource location, a referencesignal frequency domain resource location, or a reference signalconfiguration index. The reference signal sending indication is used toindicate sending of the first reference signal, the reference signalperiod is used to indicate a sending period of the reference signal (onthe premise that the reference signal is sent periodically), and thereference signal configuration index is used to indicate a location ofreference signal configuration information.

In an optional design, the first configuration information includes atleast a reference signal sending time, and the reference signal sendingtime is used to indicate a sending time at which the access networkdevice sends the first reference signal. In this design, the terminaldevice can detect the first reference signal according to the referencesignal sending time.

Optionally, the reference signal sending time may be a time differencebetween a time at which the access network device sends the firstreference signal and a time at which the access network device sends theactivation command. In this way, the terminal device may determine thesending time of the first reference signal according to a receiving timeof the activation command, and then perform corresponding measurement.For example, the reference signal sending time is a subframe offsetvalue of the sending time of the first reference signal relative to thesending time of the activation command. If the value is 2, it indicatesthat the sending time of the first reference signal is after twosubframes of the sending time of the activation command.

Optionally, the reference signal sending time may alternatively be anabsolute time at which the access network device sends the firstreference signal, for example, a number of a subframe or a frame of thefirst reference signal. The terminal device may receive and measure thereference signal according to the sending time. This is not specificallylimited herein. For example, the reference signal sending time is aframe number and/or a subframe number of a radio frame in which theaccess network device sends the first reference signal.

For example, if the first configuration information further includes atime domain resource location and/or a frequency domain resourcelocation of the first reference signal, the time domain resourcelocation and/or the frequency domain resource location of the firstreference signal are/is a time domain resource location and/or afrequency domain resource location at which the access network devicesends the first reference signal. The terminal device may measure thereference signal according to the sending time and the time domainresource location and/or the frequency domain resource location of thefirst reference signal. If the first configuration information does notinclude the time domain resource location and/or the frequency domainresource location of the first reference signal, the terminal device mayreceive the reference signal according to the reference signal sendingtime in a detection manner similar to that in prior approaches, forexample, blind detection. This is not specifically limited herein.

Optionally, the time domain resource location may be a symbol location,for example, a location of an orthogonal frequency-division multiplexing(OFDM) symbol, and/or the frequency domain resource location may be aquantity of carriers or subcarriers and/or locations of the carriers orsubcarriers.

For another example, when the first reference signal is a periodicreference signal, the first configuration information may furtherinclude a reference signal period, so that the terminal device canobtain a sending period of the first reference signal, and measure theperiodically sent first reference signal according to the referencesignal sending time and the reference signal sending period. Further,the first configuration information may further include a time domainresource location and/or a frequency domain resource location of thereference signal.

For still another example, when the first reference signal is anadditional reference signal such as a CSI-RS, the first configurationinformation may include a reference signal configuration index. Thereference signal configuration index is used to indicate a location ofreference signal configuration information. The reference signalconfiguration index corresponds to the reference signal configurationinformation. In other words, each reference signal configuration indexcorresponds to one group of reference signal configuration information.For example, a reference signal configuration index 1 corresponds to oneor more of a first sending time, a first time domain resource location,a first frequency domain resource location, and a first period of areference signal, and a reference signal configuration index 2corresponds to one or more of a second sending time, a second timedomain resource location, a second frequency domain resource location,and a second period of the reference signal. A correspondence betweenthe reference signal configuration index and the reference signalconfiguration information is notified to the terminal device in advance.A specific notification manner may be common signaling or dedicatedsignaling. This is not specifically limited herein. The firstconfiguration information includes the reference signal configurationindex, so that signaling load for sending the first configurationinformation can be reduced. It should be noted herein that the firstconfiguration information may include only the reference signalconfiguration index, and the terminal device obtains the configurationinformation of the first reference signal according to the receivedreference signal configuration index, to receive and measure the firstreference signal.

In another optional design, the first configuration information includesat least a reference signal sending indication, and the reference signalsending indication is used to indicate sending of the first referencesignal. In this design, the terminal device may receive and measure thefirst reference signal according to at least the sending indication in adetection manner similar to that in prior approaches, for example, blinddetection.

Optionally, the first configuration information includes only areference signal sending indication, and the terminal device detects andmeasures the first reference signal in a blind detection manner. Theblind detection herein may be blind detection in prior approaches. Anexample in which the first reference signal is a synchronization signalis used. The terminal device may start to detect the synchronizationsignal according to a predefined synchronization signal sequence. Whendetermining that the synchronization signal is detected, the terminaldevice measures the synchronization signal. A manner of “detecting thesynchronization signal” mentioned herein may be the same as that ofdetecting the synchronization signal in prior approaches. For example,correlation processing may be performed according to the predefinedsynchronization signal sequence and a received sequence, and it isdetermined, according to a peak value of a correlation result, that thesynchronization signal is detected.

Optionally, the first configuration information further includes one ormore of a reference signal sending time, a reference signal period, areference signal time domain resource location, a reference signalfrequency domain resource location, and a reference signal configurationindex.

In still another optional design, the first configuration informationincludes a first part and a second part. The first part may include oneor more of a reference signal sending indication, a reference signalsending time, a reference signal period, a reference signal time domainresource location, a reference signal frequency domain resourcelocation, and a reference signal configuration index. The second partmay include one or more of a reference signal sending indication, areference signal sending time, a reference signal period, a referencesignal time domain resource location, a reference signal frequencydomain resource location, and a reference signal configuration index.However, content included in the first part and content included in thesecond part do not overlap.

For example, the first part includes the reference signal sendingindication, and the access network device sends the first part and theactivation command at the same time. The second part includes one ormore of the reference signal sending time, the reference signal period,the reference signal time domain resource location, the reference signalfrequency domain resource location, and the reference signalconfiguration index, and the access network device sends the second partbefore the activation command. In this design, the terminal device firstobtains the second part of the first configuration information,determines one or more of the reference signal sending time, thereference signal period, the reference signal time domain resourcelocation, the reference signal frequency domain resource location, andthe reference signal configuration index of the reference signal, anddetermines, according to the reference signal sending indication sent atthe same time as the activation command, that the access network devicesends the first reference signal, and receives and measures the firstreference signal according to the previously received second part of thefirst configuration information.

For another example, the first part includes the reference signalsending time, and the access network device sends the first part and theactivation command at the same time. The second part includes one ormore of the reference signal period, the reference signal time domainresource location, the reference signal frequency domain resourcelocation, and the reference signal configuration index, and the accessnetwork device sends the second part before the activation command. Inthis design, the terminal device first obtains the second part of thefirst configuration information, determines one or more of the referencesignal period, the reference signal time domain resource location, thereference signal frequency domain resource location, and the referencesignal configuration index, and determines, according to the referencesignal sending time sent at the same time as the activation command,that the access network device sends the first reference signal, andreceives and measures the first reference signal according to thepreviously received second part of the first configuration information.

Further, a beamforming technology is used in the NR system, and one cellmay correspond to a plurality of beams. When the access network deviceneeds to activate the secondary cell, a reference signal block needs tobe separately sent on the plurality of beams corresponding to thesecondary cell. The following further describes the secondimplementation of the present invention with reference to FIG. 4 byusing an example in which the first reference signal is asynchronization signal. The following description is also applicable tothe content related to sending of the first reference signal in thefirst implementation of the present invention. A difference lies inthat, in the first implementation of the present invention, temporarysending of the reference signal is not mentioned, and the firstconfiguration information does not need to be additionally notified, butonly sending of the second configuration information is mentioned.

A to-be-activated secondary cell may correspond to a plurality of beams,and the access network device needs to send a reference signal on atleast one of the plurality of beams, to activate the secondary cell. Itshould be noted herein that the access network device may send thereference signal on all the beams corresponding to the secondary cell,so that the terminal device performs measurement, or may determine someof the beams to send the reference signal. For determining of a beam onwhich the reference signal is sent, optionally, the access networkdevice may estimate an approximate geographic location of the terminaldevice according to a location of a beam that is in a primary cell oranother secondary cell in an active state and that serves the terminaldevice, and determine at least one beam in the plurality of beamscorresponding to the secondary cell. A location of the determined atleast one beam is close to the estimated location of the terminaldevice. The access network device may alternatively select ato-be-measured beam in another manner. This is not specifically limitedherein.

In an optional design, in step 303, the first reference signal is asynchronization signal, the synchronization signal includes at least onesynchronization signal block, and the first configuration informationsent by the access network device to the terminal device includesconfiguration information of the at least one synchronization signalblock. The configuration information of each synchronization signalblock is used to indicate configuration information of a synchronizationsignal block sent by the access network device on a corresponding beam.

Further, in step 305, the access network device sends, to the terminaldevice according to the first configuration information, a correspondingsynchronization signal block on the at least one beam corresponding tothe to-be-activated secondary cell. Correspondingly, in step 304, theterminal device measures the detected at least one synchronizationsignal block, to obtain a corresponding channel measurement result. Instep 307, the terminal device may send channel measurement results ofall detected synchronization signal blocks to the access network device,or may feed back some channel measurement results indicating goodchannel quality. For example, only a measurement result indicating bestchannel quality may be fed back, so that the access network device candetermine a beam location or an approximate geographic orientation ofthe terminal device. The following further describes step 307.

Further, optionally, in the first and the second implementations of thepresent invention, in step 306, that the terminal device measures thefirst reference signal according to the first configuration informationspecifically includes: The terminal device measures signal quality ofthe first reference signal.

Optionally, the signal quality measurement result may include one ormore of reference signal received power (RSRP), a reference signalstrength indicator (RSSI), reference signal received quality (RSRQ), anda signal to interference plus noise ratio (SINR). The signal qualitymeasurement result may alternatively be other information for measuringsignal quality in prior approaches. This is not specifically limitedherein.

Further, optionally, in the first and the second implementations of thisembodiment, in step 307, the terminal device sends the measurementresult to the access network device in a manner that includes but is notlimited to the following sending manners:

In a first implementation, the terminal device sends, according to apreset reporting time, the measurement result to the access networkdevice when the reporting time arrives. The preset reporting time may bepreconfigured by the access network device for the terminal device, ormay be specified in a protocol or standard, or may be notified to theterminal device in another manner. In addition, the reporting time maybe periodic, or may be dynamically configured. This is not limitedherein. Optionally, the terminal may further send both the measuredfirst reference signal or reference signal block and the measurementresult to the access network device.

In a second implementation, when determining that the channelmeasurement result is greater than a specified threshold, the terminaldevice sends the measurement result to the access network device. Thespecified threshold may be determined according to an actualrequirement, or may be determined according to an event in a wirelesssystem. This is not limited herein.

In addition, the foregoing two implementations may be used incombination.

The solutions provided in the embodiments of the present invention aremainly described above from a perspective of interaction between networkelements. It can be understood that, to implement the foregoingfunctions, the network elements such as the terminal device and theaccess network device include a corresponding hardware structure and/orsoftware module for performing each of the functions. A person skilledin the art should easily be aware that, in combination with the examplesdescribed in the embodiments disclosed in this specification, units, andalgorithms steps may be implemented by hardware or a combination ofhardware and computer software in the present invention. Whether afunction is performed by hardware or hardware driven by computersoftware depends on particular applications and design constraints ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the present invention.

FIG. 6 is a schematic structural diagram of an access network deviceaccording to an embodiment. The access network device 600 includes aprocessor 601 and a transmitter 602. The access network device furtherincludes a memory 604 according to an actual requirement.

The processor 601 is configured to determine first configurationinformation of a first reference signal.

The transmitter 602 is configured to send an activation command to aterminal device, and the activation command is used to indicateactivating a secondary cell.

The transmitter 602 is further configured to send the firstconfiguration information of the first reference signal that isdetermined by the processor to the terminal device.

The transmitter 602 is further configured to send the first referencesignal to the terminal device according to the first configurationinformation, and the first reference signal is used to obtain a channelmeasurement result of the secondary cell.

Optionally, the access network device further includes a receiver 603,and the receiver 603 is configured to receive the channel measurementresult from the terminal device.

Specifically, the first reference signal is located before an availablesecond reference signal of the terminal device in time domain, and thesecond reference signal is configured by using second configurationinformation; or the first reference signal is located between twoadjacent second reference signals of the terminal device in time domain,and the two adjacent second reference signals are configured by usingsame second configuration information. Optionally, the second referencesignal is periodic.

In an optional design, the first reference signal is a synchronizationsignal or a channel state information reference signal. For example, ifthe processor determines that the terminal device is not synchronizedwith the secondary cell, the reference signal is a synchronizationsignal; or if the processor determines that the terminal device issynchronized with the secondary cell, the reference signal is a channelstate information reference signal.

In an optional design, the first configuration information is includedin the activation command; or the first configuration information issent before the activation command; or a first part of the firstconfiguration information is included in the activation command, and asecond part of the first configuration information is sent before theactivation command.

In an optional design, before the transmitter sends the first referencesignal to the terminal device according to the first configurationinformation,

-   -   when the processor determines that a difference between the        available second reference signal of the terminal device and a        current time exceeds a first threshold, the processor determines        that the first reference signal is sent to the terminal device,        where the first threshold is preset.

Further, the first configuration information includes at least one ofthe following information:

-   -   a reference signal sending indication;    -   a reference signal sending time;    -   a reference signal period;    -   a reference signal time domain resource location;    -   a reference signal frequency domain resource location; and    -   a reference signal configuration index, where the reference        signal configuration index is used to indicate a location of        reference signal configuration information.

The reference signal sending time of the first reference signal is arelative time difference between a time at which the transmitter sendsthe first reference signal and a time at which the transmitter sends theactivation command, or is a time at which the transmitter sends thefirst reference signal.

It should be noted that, for a specific implementation of performing thesecondary cell activation method by the access network device 600, referto the description of the secondary cell activation method provided inthe foregoing embodiment of the present invention. The access networkdevice 600 in this embodiment of the present invention and the secondarycell activation method corresponding to FIG. 3 are according to a sameconcept, and technical effects brought by the access network device 600are the same as those brought by the foregoing resource schedulingmethod. Specific functions of the processor 601, the transmitter 602,the receiver 603, and the memory 604 that are included in the accessnetwork device in this embodiment, and any features, terms, andimplementation details thereof correspond to functions of the accessnetwork device in the method embodiment corresponding to FIG. 3. Forspecific content, refer to the description of the method embodimentcorresponding to FIG. 3 of the present invention. Details are notdescribed herein again.

It should be noted that, in the foregoing embodiment, the access networkdevice may be completely or partially implemented by software, hardware,firmware, or any combination thereof.

In an optional manner, a corresponding component in the foregoingembodiment may be implemented by corresponding hardware, or may beimplemented by corresponding hardware by executing correspondingsoftware. For example, the receiver 604 may be hardware that has theforegoing receiving function, for example, a transceiver that integratesreceiving and sending functions or a receiver that implements only areceiving function, or may be a general processor or another hardwaredevice that can execute a corresponding computer program to implementthe foregoing function, or may be a software module or a functional unitthat implements a corresponding function, for example, a receiving unit.For another example, the processor 601 may be hardware that has aprocessor function, for example, a processor having a specific functionor a general processor, or may be another hardware device that canexecute a corresponding computer program to implement the foregoingfunction, or may be a software module or a functional unit thatimplements a corresponding function, for example, a processing unit. Forstill another example, the transmitter 602 may be hardware that has theforegoing sending function, for example, a transceiver that integratesreceiving and sending functions, or a transmitter that implements only asending function, or may be a general processor or another hardwaredevice that can execute a corresponding computer program to implementthe foregoing function, or may be a software module or a functional unitthat implements a corresponding function, for example, a sending unit.

FIG. 7 is a schematic structural diagram of another access networkdevice according to an embodiment of the present invention. The accessnetwork device includes a processing unit 701 and a sending unit 702.The access network device further includes a storage unit 704 accordingto an actual requirement.

The processing unit 701 is configured to determine first configurationinformation of a first reference signal.

The sending unit 702 is configured to send an activation command to aterminal device, and the activation command is used to indicateactivating a secondary cell.

The sending unit 702 is further configured to send the firstconfiguration information of the first reference signal that isdetermined by the processing unit to the terminal device.

The sending unit 702 is further configured to send the first referencesignal to the terminal device according to the first configurationinformation, and the first reference signal is used to obtain a channelmeasurement result of the secondary cell.

Optionally, the access network device further includes a receiving unit703, and the receiving unit 703 is configured to receive the channelmeasurement result from the terminal device.

It should be noted that, for a specific implementation of performing thesecondary cell activation method by the access network device 700, referto the description of the secondary cell activation method provided inthe foregoing embodiment of the present invention. The access networkdevice 700 in this embodiment of the present invention and the secondarycell activation method corresponding to FIG. 3 are according to a sameconcept, and technical effects brought by the access network device 700are the same as those brought by the foregoing resource schedulingmethod. Specific functions of the processing unit 701, the sending unit702, the receiving unit 703, and the storage unit 704 that are includedin the access network device in this embodiment, and any features,terms, and implementation details thereof correspond to functions of theaccess network device in the method embodiment corresponding to FIG. 3.For specific content, refer to the description of the method embodimentcorresponding to FIG. 3 of the present invention. Details are notdescribed herein again.

In another optional manner, when the access network device isimplemented by software, the access network device may be completely orpartially implemented in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instructions are loaded or executed on acomputer, some or all of the procedures or functions in the embodimentsof the present invention are implemented. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, oranother programmable apparatus. The computer instructions may be storedin a computer-readable storage medium, or may be transmitted from onecomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted fromone website, computer, server, or data center to another website,computer, server, or data center in a wired (for example, a coaxialcable, an optical fiber, or a digital subscriber line (DSL)) or wireless(for example, infrared, radio, or microwave) manner. Thecomputer-readable storage medium may be any usable medium accessible bythe computer, or a data storage device such as a server or a data centerthat integrates one or more usable media. The usable medium may be amagnetic medium (for example, a floppy disk, a hard disk, or a magnetictape), an optical medium (for example, a digital video disk (DVD)), asemiconductor medium (for example, a solid state disk Solid State Disk(SSD)), or the like.

FIG. 8 is a schematic structural diagram of a communications apparatusaccording to an embodiment. The communications apparatus 800 may be aterminal device, or another hardware device, a functional module, achip, or the like that can be configured to communicate with an accessnetwork device to implement a corresponding function. The communicationsapparatus includes a processor 801 and a receiver 802. Thecommunications apparatus further includes a memory 804 according to anactual requirement.

The receiver 802 is configured to receive an activation command from anaccess network device, and the activation command is used to indicateactivating a secondary cell.

The receiver 802 is further configured to: receive first configurationinformation of a first reference signal from the access network device,and receive the first reference signal according to the firstconfiguration information.

The processor 801 is configured to obtain a channel measurement resultof the secondary cell according to the first reference signal.

Optionally, the communications apparatus further includes a transmitter803, and the transmitter is configured to send the channel measurementresult to the access network device.

Specifically, the first reference signal is located before an availablesecond reference signal of the terminal device in time domain, and thesecond reference signal is configured by using second configurationinformation; or the first reference signal is located between twoadjacent second reference signals of the terminal device in time domain,and the two adjacent second reference signals are configured by usingsame second configuration information. Optionally, the second referencesignal is periodic.

In an optional design, the first reference signal is a synchronizationsignal or a channel state information reference signal. For example, ifthe processor determines that the terminal device is not synchronizedwith the secondary cell, the reference signal is a synchronizationsignal; or if the processor determines that the terminal device issynchronized with the secondary cell, the reference signal is a channelstate information reference signal.

In an optional design, the first configuration information is includedin the activation command; or the first configuration information issent before the activation command; or a first part of the firstconfiguration information is included in the activation command, and asecond part of the first configuration information is sent before theactivation command.

Further, the first configuration information includes at least one ofthe following information:

-   -   a reference signal sending indication;    -   a reference signal sending time;    -   a reference signal period;    -   a reference signal time domain resource location;    -   a reference signal frequency domain resource location; and    -   a reference signal configuration index, where the reference        signal configuration index is used to indicate a location of        reference signal configuration information.

The reference signal sending time of the first reference signal is arelative time difference between a time at which the access networkdevice sends the first reference signal and a time at which the accessnetwork device sends the activation command, or is a time at which theaccess network device sends the first reference signal.

It should be noted that, for a specific implementation of performing thesecondary cell activation method by the communications apparatus 800,refer to the description of the secondary cell activation methodprovided in the foregoing embodiment of the present invention. Thecommunications apparatus 800 in this embodiment of the present inventionand the secondary cell activation method corresponding to FIG. 4 areaccording to a same concept, and technical effects brought by thecommunications apparatus 800 are the same as those brought by theforegoing resource scheduling method. Specific functions of theprocessor 801, the receiver 802, the transmitter 803, and the memory 804that are included in the communication apparatus in this embodiment, andany features, terms, and implementation details thereof correspond tothe functions of the terminal device in the method embodimentcorresponding to FIG. 3. For specific content, refer to the descriptionof the method embodiment corresponding to FIG. 3 of the presentinvention. Details are not described herein again.

It should be noted that, in the foregoing embodiment, the terminaldevice may be completely or partially implemented by software, hardware,firmware, or any combination thereof.

In an optional manner, a corresponding component in the foregoingembodiment may be implemented by corresponding hardware, or may beimplemented by corresponding hardware by executing correspondingsoftware. For example, the receiver 802 may be hardware that has theforegoing receiving function, for example, a transceiver that integratesreceiving and sending functions or a receiver that implements only areceiving function, or may be a general processor or another hardwaredevice that can execute a corresponding computer program to implementthe foregoing function, or may be a software module or a functional unitthat implements a corresponding function, for example, a receiving unit.For another example, the processor 801 may be hardware that has aprocessor function, for example, a processor having a specific functionor a general processor, or may be another hardware device that canexecute a corresponding computer program to implement the foregoingfunction, or may be a software module or a functional unit thatimplements a corresponding function, for example, a processing unit. Forstill another example, the transmitter 803 may be hardware that has theforegoing sending function, for example, a transceiver that integratesreceiving and sending functions, or a transmitter that implements only asending function, or may be a general processor or another hardwaredevice that can execute a corresponding computer program to implementthe foregoing function, or may be a software module or a functional unitthat implements a corresponding function, for example, a sending unit.

FIG. 9 is a structural diagram of another communications apparatus 900according to an embodiment of the present invention. The communicationsapparatus includes a processing unit 901 and a receiving unit 902. Theaccess network device further includes a storage unit 904 according toan actual requirement.

The receiving unit 902 is configured to receive an activation commandfrom an access network device, and the activation command is used toindicate activating a secondary cell.

The receiving unit 902 is further configured to: receive firstconfiguration information of a first reference signal from the accessnetwork device, and receive the first reference signal according to thefirst configuration information.

The processing unit 901 is configured to obtain a channel measurementresult of the secondary cell according to the first reference signal.

Optionally, the communications apparatus further includes a sending unit903, and the sending unit 903 is configured to send the channelmeasurement result to the access network device.

Specifically, the first reference signal is located before an availablesecond reference signal of the terminal device in time domain, and thesecond reference signal is configured by using second configurationinformation; or the first reference signal is located between twoadjacent second reference signals of the terminal device in time domain,and the two adjacent second reference signals are configured by usingsame second configuration information. Optionally, the second referencesignal is periodic.

It should be noted that, for a specific implementation of performing thesecondary cell activation method by the communications apparatus 900,refer to the description of the secondary cell activation methodprovided in the foregoing embodiment of the present invention. Thecommunications apparatus 900 in this embodiment of the present inventionand the secondary cell activation method corresponding to FIG. 4 areaccording to a same concept, and technical effects brought by thecommunications apparatus 900 are the same as those brought by theforegoing resource scheduling method. Specific functions of theprocessing unit 901, the receiving unit 902, the sending unit 903, andthe storage unit 904 that are included in the communications apparatusin this embodiment, and any features, terms, and implementation detailsthereof correspond to functions of the terminal device in the methodembodiment corresponding to FIG. 3. For specific content, refer to thedescription of the method embodiment corresponding to FIG. 3 of thepresent invention. Details are not described herein again.

In another optional manner, when the communications apparatus isimplemented by software, the communications apparatus may be completelyor partially implemented in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instructions are loaded or executed on acomputer, some or all of the procedures or functions in the embodimentsof the present invention are implemented. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, oranother programmable apparatus. The computer instructions may be storedin a computer-readable storage medium, or may be transmitted from onecomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted fromone website, computer, server, or data center to another website,computer, server, or data center in a wired (for example, a coaxialcable, an optical fiber, or a digital subscriber line (DSL)) or wireless(for example, infrared, radio, or microwave) manner. Thecomputer-readable storage medium may be any usable medium accessible bythe computer, or a data storage device such as a server or a data centerthat integrates one or more usable media. The usable medium may be amagnetic medium (for example, a floppy disk, a hard disk, or a magnetictape), an optical medium (for example, a digital video disk (DVD)), asemiconductor medium (for example, a solid state disk Solid State Disk(SSD)), or the like.

It should be noted that the processor included in the access networkdevice or the communications apparatus configured to perform thesecondary cell activation method provided in the embodiments of thepresent invention may be a central processing unit (CPU), ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field programmablegate array (FPGA) or another programmable logical device, a transistorlogical device, a hardware component, or any combination thereof. Theprocessor may implement or execute various example logical blocks,modules, and circuits described with reference to content disclosed inthe present invention. The processor may alternatively be a combinationof processors implementing a computing function, for example, acombination of one or more microprocessors, or a combination of the DSPand a microprocessor.

Method or algorithm steps described in combination with the embodimentsof the present invention may be implemented by hardware, or may beimplemented by a processor by executing a software instruction. Thesoftware instruction may include a corresponding software module. Thesoftware module may be stored in a RAM memory, a flash memory, a ROMmemory, an EPROM memory, an EEPROM memory, a register, a hard disk, aremovable magnetic disk, a CD-ROM, or a storage medium of any other formknown in the art. An example storage medium is coupled to a processor,so that the processor can read information from the storage medium andwrite information into the storage medium. Certainly, the storage mediummay be a component of the processor. The processor and the storagemedium may be located in an ASIC. In addition, the ASIC may be locatedin a terminal device. Certainly, the processor and the storage mediummay alternatively exist in the terminal device as discrete components.

It may be understood that FIG. 6 to FIG. 9 merely show a simplifieddesign of the access network device or the communications apparatus. Inactual application, the access network device or the communicationsapparatus may include any quantity of transmitters, receivers,processors, controllers, memories, communications units, and the like.

An embodiment of the present invention further provides a communicationssystem, including at least one access network device and at least onecommunications apparatus for executing the embodiments of the presentinvention.

It should be understood that “an embodiment”, “one embodiment”, or “thisembodiment of the present invention” mentioned in the entirespecification means that particular features, structures, orcharacteristics related to the embodiment are included in at least oneembodiment of the present invention. Therefore, “in an embodiment”, “inone embodiment”, or “in this embodiment of the present invention”appearing throughout the specification does not necessarily refer to asame embodiment. In addition, these particular features, structures, orcharacteristics may be combined in one or more embodiments in anyappropriate manner.

It should be understood that sequence numbers of the foregoing processesdo not mean an execution sequence in the embodiments of the presentinvention. The execution sequence of the processes should be determinedaccording to functions and internal logic of the processes, and shouldnot be construed as any limitation on the implementation processes ofthe embodiments of the present invention.

The objectives, technical solutions, and beneficial effects of thepresent invention are further described in detail in the foregoingspecific implementations. It should be understood that the foregoingdescriptions are merely specific implementations of the presentinvention, but are not intended to limit the protection scope of thepresent invention. Any modification, equivalent replacement, orimprovement made according to the technical solutions of the presentinvention shall fall within the protection scope of the presentinvention.

The solutions provided in the embodiments of the present invention aremainly described above from a perspective of interaction between networkelements. It can be understood that, to implement the foregoingfunctions, the network elements such as the communications apparatus andthe radio access network device include a corresponding hardwarestructure and/or software module for performing each of the functions. Aperson skilled in the art should easily be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units, and algorithm steps may be implemented by hardwareor a combination of hardware and computer software in the presentinvention. Whether a function is performed by hardware or hardwaredriven by computer software depends on particular applications anddesign constraints of the technical solutions. A person skilled in theart may use different methods to implement the described functions foreach particular application, but it should not be considered that theimplementation goes beyond the scope of the present invention.

The foregoing descriptions are merely specific implementations of thepresent invention, but are not intended to limit the protection scope ofthe present invention. Any variation or replacement readily figured outby a person skilled in the art within the technical scope disclosed inthe present invention shall fall within the protection scope of thepresent invention. Therefore, the protection scope of the presentinvention shall be subject to the protection scope of the claims.

What is claimed is:
 1. A secondary cell activation method, comprising:sending, by an access network device, an activation command to aterminal device, wherein the activation command indicates activating asecondary cell; sending, by the access network device, firstconfiguration information of a first reference signal to the terminaldevice; and sending, by the access network device, the first referencesignal to the terminal device according to the first configurationinformation, wherein the first reference signal is used to obtain achannel measurement result of the secondary cell.
 2. The methodaccording to claim 1, wherein the first reference signal is locatedbefore an available second reference signal of the terminal device in atime domain, and the second reference signal is configured using secondconfiguration information; or the first reference signal is locatedbetween two adjacent second reference signals of the terminal device inthe time domain, and the two adjacent second reference signals areconfigured using same second configuration information.
 3. The methodaccording to claim 1, wherein: the activation command comprises thefirst configuration information; or the access network device sends thefirst configuration information before the activation command; or theactivation command comprises a first part of the first configurationinformation, and the access network device sends a second part of thefirst configuration information before the activation command.
 4. Themethod according to claim 1, wherein the first configuration informationcomprises at least one of the following information: a reference signalsending indication; a reference signal sending time; a reference signalperiod; a reference signal time domain resource location; a referencesignal frequency domain resource location; and a reference signalconfiguration index, wherein the reference signal configuration indexindicates a location of reference signal configuration information. 5.The method according to claim 4, wherein the reference signal sendingtime of the first reference signal is a relative time difference betweena time at which the access network device sends the first referencesignal and a time at which the access network device sends theactivation command, or is a time at which the access network devicesends the first reference signal.
 6. The method according to claim 1,wherein before the sending, by the access network device, the firstreference signal to the terminal device according to the configurationinformation, the method further comprises: when a difference between apreset time at which the available second reference signal of theterminal device is sent and a current time exceeds a first threshold,determining, by the access network device, to send the first referencesignal to the terminal device, wherein the first threshold is preset. 7.A secondary cell activation method, comprising: receiving, by a terminaldevice, an activation command from an access network device, wherein theactivation command indicates activating a secondary cell; receiving, bythe terminal device, first configuration information of a firstreference signal from the access network device; and receiving, by theterminal device, the first reference signal according to the firstconfiguration information, and obtaining a channel measurement result ofthe secondary cell according to the first reference signal.
 8. Themethod according to claim 7, wherein: the activation command comprisesthe first configuration information; or the terminal device receives thefirst configuration information before the activation command; or theactivation command comprises a first part of the first configurationinformation, and the terminal device receives a second part of the firstconfiguration information before the activation command.
 9. The methodaccording to claim 7, wherein the first configuration informationcomprises at least one of the following information: a reference signalsending indication; a reference signal sending time; a reference signalperiod; a reference signal time domain resource location; a referencesignal frequency domain resource location; and a reference signalconfiguration index, wherein the reference signal configuration indexindicates a location of reference signal configuration information. 10.The method according to claim 9, wherein the reference signal sendingtime of the first reference signal is a time difference between a timeat which the access network device sends the first reference signal anda time at which the access network device sends the activation command,or is a time at which the access network device sends the firstreference signal.
 11. An apparatus, comprising: one or more processors,and a non-transitory storage medium configured to store programinstructions, which when executed by the one or more processors, theprogram instructions cause the apparatus to perform a method thatcomprises: determining first configuration information of a firstreference signal; sending an activation command to a terminal device,wherein the activation command indicates activating a secondary cell;sending the first configuration information of the first referencesignal that is determined by the processor to the terminal device; andsending the first reference signal to the terminal device according tothe first configuration information, wherein the first reference signalis used to obtain a channel measurement result of the secondary cell.12. The apparatus according to claim 11, wherein: the activation commandcomprises the first configuration information; or the apparatus sendsthe first configuration information before the activation command; orthe activation command comprises a first part of the first configurationinformation, and the apparatus sends a second part of the firstconfiguration information before the activation command.
 13. Theapparatus according to claim 11, wherein the first configurationinformation comprises at least one of the following information: areference signal sending indication; a reference signal sending time; areference signal period; a reference signal time domain resourcelocation; a reference signal frequency domain resource location; and areference signal configuration index, wherein the reference signalconfiguration index indicates a location of reference signalconfiguration information.
 14. The apparatus according to claim 13,wherein the reference signal sending time of the first reference signalis a relative time difference between a time at which the transmittersends the first reference signal and a time at which the transmittersends the activation command, or is a time at which the transmittersends the first reference signal.
 15. The apparatus according to claim11, wherein the method further comprises: when determining that adifference between a preset time at which the available second referencesignal of the terminal device is sent and a current time exceeds a firstthreshold, determining that the first reference signal is sent to theterminal device, wherein the first threshold is preset.